Current static needle insertion planning uses a preoperative image of the region of interest including the point of entry, the target and any obstacles en route which have to be avoided. An obstacle can be understood to mean a real physical obstacle, such as a rib, or it can mean a sensitive area where damage could be caused by entry of the needle, such as a major blood vessel or an important nerve. The problem is that this procedure does not take into account cyclical motion of the patient, such as from breathing, which could cause the entry point, the target point and the position of any obstacles en route to move in some sort of reproducible cycle from their initial positions relative to each other.
In existing methods, the progress of the needle (or of the process) is reviewed intraoperatively and the images are synchronized to the motion cycle, and then appropriate correction is taken during the motion cycle. This is the method used in following heart motion and pulsating arteries during angioplasty, or during valve correction operations, with the heart beat continuing during the procedure. Such methods have a serious disadvantage in that they require constant, generally fluoroscopic, imaging during the complete duration of the procedure, with concomitant significant radiation exposure for the patient and the medical staff. In other known methods, such as that shown in U.S. Pat. No. 7,833,221 to J. W. Voegele et al, for “System and Method for Treatment of Tissue using the Tissue as a Fiducial”, there is described an ultrasound method in which the respiration cycle is monitored to indicate when a tissue target is approaching the dwell position—the brief pause between inhalation and exhalation in each respiratory cycle—so that the surgeon can insert his surgical device to a tumor when the tumor is positioned according to an image of the tumor generated at the dwell position. However, such methods limit insertion of a tool to a single target point imaged non-iteratively at a repeated fixed point in the breathing cycle. Further, in some existing methods, as disclosed, for example, in U.S. Pat. No. 7,008,373 to Stoianovici et al, for “System and method for robot targeting under fluoroscopy based on image serving”, it is preferred that patient respiration is shortly stopped during the image acquisition prior to target selection and during needle insertion, thus requiring the physician to rely solely on the patient's ability to hold his breath at the required times and for the required durations.